ABSTRACT Two field experiments were conducted at National Agricultural Research Centre, Islamabad during spring seasons 2002-03 to evaluate response of sunflower (Helianthus annus L.) to different levels of zinc and iron under irrigated conditions. Three levels of zinc 0, 5 and 10 kg ha-1 and three levels of iron 0, 2.5 and 5 kg ha-1 were applied in soil to see their effect alone and in different combination on grain yield, oil contents, other agronomic parameters and concentrations of zinc and iron in leaves of sunflower. Highest grain yields (2743 kg ha-1) and 1000-seed weight were obtained in treatment that received combined application of 10 kg zinc and 5 kg iron ha-1. Addition of 0, 2.5 and 5.0 kg ha-1 iron and 5.0 kg ha-1 zinc alone increased yield non-significantly as compared to control. The combined application of zinc + iron at 5.0 kg ha-1 produced significantly (P ≤ 0.05) higher yield than control but was similar to the lower doses. Highest plant height (167.0cm) and greater head diameter (17.6 cm) and highest oil contents (39.7%) were achieved with the application of 10 kg zinc and 5 kg Iron ha-1. The concentrations of zinc and total iron in the leaves were increased with zinc and iron application. Maximum concentration of zinc (70.5 mg kg -1) and iron (553.5 mg kg -1) in leaves was recorded with application of 10 kg zinc + 5 kg iron ha-1. The results of this study suggest that soil application of 10 kg zinc and 5 kg iron ha-1 has a positive affect, both quantitative and qualitative on yield of sunflower under irrigated conditions. Key Words: Sunflower, Zinc, Iron, Irrigated Alkaline Soils, Yield, Quality Citation: M.A. Khan, J. Din, S. Nasreen, M.Y. Khan, S.U. Khan and A.R. Gurmani. 2009. Response of sunflower to different levels of Zinc and Iron under irrigated conditions. Sarhad J. Agric. 25(2): 159-163. INTRODUTION Sunflower (Helianthus annus L.) being one of the most important sources of high quality edible oil has been identified to be a potential oilseed crop for dry land regions. The sunflower plant has a good rooting system which enables it to do well even under poor soil conditions (Andria et al. 1995). Research in Pakistan (Rashid, 1996) and elsewhere (Takkar and Walker, 1993) has revealed that micronutrient deficiency especially zinc and iron (Amin et al. 2001) is a major micronutrient disorder in alkaline calcareous soils because of low zinc and iron availability in such soils (Marschner, 1995). Deficiency of any micronutrient adversely affects plant growth, development and ultimately yields, thus minimizes the usefulness of other agricultural inputs including N, P and K fertilizer, the efficiency of which can substantially be increased by application of micronutrients zinc and iron (Amin et al. 2001, El-Fouly et al. 2001, Gill et al. 2004). A significant increase in grain yield, protein and oil contents of sunflower due to zinc application has been reported (Khurana and Chatterjee, 2001). The availability of mineral nutrients in the soil solution mainly depends on the soil pH, redox potential, organic matter contents and fertilizer application (Marschner, 1995). The absorption from soil by the plant root depends on the nutrient concentration in soil solution as well as root morphology and physiology. Soils of arid and semi-arid areas are characterized by high pH and low organic matter which reduce the availability of micronutrient like zinc and iron to crop plants (El-Fouly, 1983). Foliar applications of micronutrients are mainly recommended. However, micronutrients application through irrigation/soil is also nowadays applied (El-Fouly et al. 2001).

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Mukhtar Ahmad Khan et al. Response of sunflower to different levels of zinc and iron …

Realizing the yield potential and the role fertilizers especially micronutrients play in sunflower production, field experiments were conducted to study the effects of zinc and iron applied as zinc sulphate and iron sulphate on yield, oil contents and other agronomic parameters of sunflower under irrigated conditions. MATERIALS AND METHODS The experiments were conducted during spring seasons 2002 and 2003 at National Agricultural Research Centre (NARC) Islamabad. Soil samples were collected from 0-30cm depth before planting from the selected sites before sowing of crop and analyzed for physico-chemical characteristics (Table I) according to the methods described by Ryan et al. (2001). The experimental sites were low in organic matter, available nitrogen, available phosphorus, zinc and Iron having pH of 7.8 (Table I). Sunflower hybrid SMH-9706 (PARSUN-2) used as a test variety was obtained from Oil Seed Program, NARC, Islamabad. Planting was done by dibbler. Plot size was 3x5 m with row to row distance of 75cm in RCBD having three replications. Basal dose of N and P was 90 kg N as urea and 60 kg P2O5 ha-1 as single superphosphate while zinc and iron rates were 0, 5 and 10 kg zinc and 0, 2.5 and 5 kg iron ha-1 as ZnSO4 7H2O and FeSO4 3H2O, applied at planting time. Table I. Physico-Chemical properties of the soil Determinations pH (Sat. paste) EC (dS m-1) Organic matter (%) CaCO3 (%) Kjeldah1 – N (%) NO3 – N (mg kg-1) N H4 – N (mg kg-1) P (mg kg-1) K (mg kg-1) Zn (mg kg-1) Fe (mg kg-1) Mn (mg kg-1) Cu (mg kg-1) Texture

Figures followed by the same letter(s) do not differ significantly at P< 0.05

Plant Height Data of plant height indicate that highest plant height was obtained in treatment that received 10 kg zinc supplemented with 5 kg iron ha-1 (Table II). Treatment of zinc alone or in combination with iron significantly (P ≤ 0.05) increased the plant height. Lowest (150.64 cm) plant height was obtained in check treatment. Increase in shoot length was recorded in bread and durum wheat (Cakmak et al. 1997), safflower and sunflower (Ismail and Azooz, 2005) with zinc application. El-Fouly et al. (2001) reported substantial increase in shoot and root length in sunflower by iron application. Head Diameter Highest (17.83 cm) head diameter was obtained in treatment that received zinc and iron at 10 kg plus 5 kg ha-1, followed by 10 kg zinc + 2.5 kg iron ha-1 and 10 kg zinc alone (Table II). Lowest (16.06 cm) head diameter was observed in control which was statistically similar to 2.5 and 5.0 kg ha-1 iron and 5 kg zinc plus 2.5 kg iron treatment. The data showed that greater increase was achieved with high dose of zinc (10 kg ha-1) alone or in combination with iron. This greater head diameter may have contributed toward over all high grain yields. Oil Content Data on oil content indicated that highest zinc alone or in combination with iron significantly increased the oil content in sunflower which was statistically similar to rest of treatments except check or only iron (Table II). Lowest oil content (37.01 %) was obtained in control treatment. Mirzapour and Khoshgoftar (2006) found significant increase in seed oil content of sunflower with 10 kg zinc ha-1 soil application. This may be due to higher assimilate supply in such condition (Khurana and Chatterjee, 2001). 1000 Seed Weight Treatment that received zinc and iron at the rate of 10kg + 5 kg ha-1 gave significantly (P ≤ 0.05) high seed weight (Table II) being different from all the treatments. The increase in sunflower head size and seed weight seems to have contributed to overall increase in grain yield. Low 1000-seed weight of sunflower in zinc-deficient conditions might have been due to impaired anther and pollen seed development, possibly as a result of decreased levels of Indole acetic acid and proteins (Brown et al. 1993). Zinc and Iron Concentration in Shoot The concentration of zinc and total iron in the leaves was increased with zinc and iron application (Fig. 1). The concentration of iron and zinc in leaves was 21.3 and 393.5 mg kg-1 respectively in control. However, these ions showed a significant (P ≤ 0.05) increase when zinc and iron rates were applied. Shanmugasundaram and Savithri (2006) recorded highest zinc content in sunflower plant with 12.5 kg ha-1 zinc sulfate application. Rashid et al.

Mukhtar Ahmad Khan et al. Response of sunflower to different levels of zinc and iron …

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(1994) found similar leaves zinc concentration with maximum grain yield in rapeseed and mustard. Increase in concentration of iron and zinc was observed particularly when zinc and iron were applied in combination. Zinc applied @ 5 kg or 10 kg ha-1 depressed iron concentration in leaves suggesting antagonism (Fig. 1b). El-Fouly et al. (2001) and Mirzapour and Khoshgoftar (2006) showed a similar trend in zinc and iron concentration in leaves with respect to zinc and iron application in sunflower. As a result of the improved status of iron status of the plants, the uptake of zinc was increased and vice versa. Similar results were obtained by Romheld et al. (1982).

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Treatments Fig. 1.

Effect of different levels of zinc and iron on concentration of zinc (a) and iron (b) in leaves of sunflower, ±-Std. Error Mean

CONCLUSION Soil application of 10 kg zinc and 5 kg iron ha-1 significantly increased seed yields and 1000-seed weight of sunflower. Plant height and greater head diameter and oil contents were achieved with 10 kg zinc and 5 kg iron ha-1. The maximum concentration of zinc and total iron in the leaves was recorded with the same treatment of zinc and iron treatment. The results of this study suggest that soil application of zinc and iron may increase both quantitative and qualitative yield of sunflower under irrigated conditions.